This invention relates to an electrical busway housing system capable of conducting electricity and mechanical connection means therefor, and more particularly, to an electrical busway housing system mechanically connected at the joints of adjoining housing sections by utilization of a coupling system having a top plate and a bottom plate, at least one of which has a roughened surface that provides superior gripping strength when the adjoining sections of busbar housing are clamped between them.
Electrical busway, also known as elongated electrical distribution busway, is well known in the art. An electrical busway housing system is typically comprised of multiple pieces of track connected end to end with one or more electrically-isolated, conductive busbars fastened to the housing, such that the system is capable of conducting electricity end to end through the busbars. The busbar is adapted to permit electrical power tap-off at any point along the length of the busbar. Such busbar is often provided overhead, or may be provided along walls or flooring, and is used to distribute electricity to various take-off devices to equipment, appliances, lighting or other articles requiring a source of electrical energy to operate. For example, when installed in a home or office setting, it is often used to permit lighting and/or electrical sockets to be placed in one or more locations along the electrical busway. When installed in a factory or other industrial application, electrical sockets, lighting or other industrial devices may be placed on, near or along the busway to obtain electrical current from the busway.
Electrical power distribution tracks or busways are typically comprised of an elongated housing containing multiple electrically isolated conductive busbars. Sections of the track can be joined together to form long runs for the power distribution, and such sections may be of any length, but are generally anywhere from two (2) to twenty (20) feet long each. The joining of two twenty foot sections to one another, for example, provides 40 feet of electrical busbar, and the process can be repeated as necessary to provide electrical busway of substantial length.
While not limited to the use of aluminum housings, aluminum busbar housing generally tends to be the housing of choice due to its light weight, great strength and economical cost and ease of manufacture.
The joining of the individual sections must provide for making both mechanical and electrical connections from one section of housing to the adjoining section. This is generally accomplished with a coupler, also known, among other terms, as a coupling system, a connecting system, a coupling assembly, or a connector assembly. There are several known approaches to this coupling system. Examples include U.S. Pat. No. 2,969,421, to Sott, Jr; U.S. Pat. No. 3,210,716 to Meacham; U.S. Pat. No. 3,509,514 to Christensen et al.; U.S. Pat. No. 6,039,584 to Ross and U.S. Pat. No. 6,105,741 to Ross, with certain of these patents focusing on the mechanical connection, the electrical connection or both.
Referring now to FIG. 1A there is illustrated a coupling system of the prior art which uses a pair of flat plate connector assemblies 2 and 4. Two sections of busway 6 and 8, shown in phantom in FIG. 1A can be connected by using the two flat plate connector assemblies 2 and 4, that sandwich a flange or similar feature at the ends 10 and 12 of the busway housing. Flat plate connector assemblies of the type of flat plate connector assemblies 2 and 4 are usually used in two sets, either top and bottom or side and side. Referring to both FIG. 1A and FIG. 1B, such flat plate connector assemblies of the type of flat plate connector assemblies 2 and 4 are each composed of a flat bottom plate 14 having a pair of throughholes 16 therethrough which may or may not be threaded, and a corresponding top plate, in this case the u-shaped top plate 18. The u-shaped top plate 18 includes throughholes 20 therethrough, which may or may not be threaded. Bolts 22 and 23 are typically inserted through the throughhole 20 and 21 respectively of u-shaped top plate 18, and into the corresponding throughhole 16 and 17 in flat bottom plate 14 whereupon, if the throughhole of the flat bottom plate is threaded, said bolt threadably engages said threaded throughhole, allowing the bolt to be tightened in order to draw the u-shaped top plate and the flat bottom plate together over the flanges at the ends 10 and 12 respectively of the busways 6 and 8. If the throughhole of the flat bottom plate 14 is not threaded, a nut 26 is threadably engaged with the bolt 22 to draw the flat bottom plate 14 and the u-shaped top plate 18 together. The frictional force between the flat bottom plate 14, the u-shaped top plate 18 and the flange of the respective housings 6 and 8 is intended to keep the adjoining housings 6 and 8 from separating. However, under loads, particularly where the housings 6 and 8 are supported overhead and span a substantial distance, the housings 6 and 8 tend to pull apart overtightening bolts 22 to provide additional compressive force generally results in stripping the threaded throughholes or nuts damaging and/or destroying the connector assembly.
Referring now to FIG. 2 there is illustrated a known wrap-around type connector 30. In this design, an aluminum extrusion 32 telescopes over the ends of housings 6 and 8 shown in phantom that are joined. Wrap-around connector 30 has two bolts 34 and 35 that tighten a plate 36 to create a frictional clamping force as described above in connection with the flat plate coupling assemblies 2 and 4. However, as may be appreciated, most of the support comes from the telescoping or wrap-a-round effect rather than the frictional clamping force.
Illustrated in FIG. 3 is yet another known connector generally referred to as a channel and set screw connector 40. An extruded piece of aluminum channel 42 is designed to slide loosely into each end of a pair of busbar housings 6 and 8 in phantom, where channels 44 and 46 engage corresponding lips on each of the busbar housings 6 and 8. Once the busway housings 6 and 8 are butted together, and the connector 40 is centered over the gap interface between the two housings 6 and 8, two or more setscrews 48 and 49 are tightened in throughholes through the connector 40 and through a corresponding channel in each housing corresponding to the lip 50 of the connector 40 in order to secure both the connector 40 and the two housings in place. Although the setscrews 48 and 49 keep the connector 40 from moving and the shape of the extrusion provides some support for keeping the two housings in line, particularly when the housings are supported overhead, the amount of gripping frictional force in this design to prevent separation of the housings is minimal.
All of the known embodiments described above suffer from the limitation that where the busbars housings are joined, particularly but not limited to larger busway systems (e.g. greater than 100 amps), where the busbar housings are installed overhead or along a wall the above described connectors provide insufficient force to hold the busbars tightly together. For example, this is particularly true for large busway systems supported overhead from a ceiling or other structure where the supports are placed at greater intervals from one another (e.g. 10 foot intervals versus 5 foot intervals). Greater spacing intervals between the supports is generally desired as fewer supports are needed to support the busway system as a whole, but as pointed out above, the known connectors between busway housing sections, particularly for the larger busway systems, cannot provide sufficient force to hold the busbar sections together over greater spacing intervals. For example, such designs typically cannot meet a United Laboratories Resistance to Bending Test 857-45, which uniformly tests the ability for such housings to withstand bending loads over such connectors.
There remains a strong felt need in the art for an electrical busbar housing system, and in particular a busbar housing coupling system that has greater resistance to bending at the joints where adjoining sections of housing are fastened together, end to end and are supported at as great an interval between supports as is practicable.
Accordingly, a primary object of this invention is to provide an electrical busway housing system that has greater strengths, greater load-carrying capabilities and greater resistance to bending, thereby enabling such housing systems to be mounted with hangers at greater intervals than are presently possible. The greater the strength of the system at a joint between adjoining housing sections, the greater the allowable distance between hangers from which the electrical busway housing system is hung.
The essence of this invention is an improved and novel coupling system. In the prior art, particularly the coupling systems illustrated in FIGS. 1A-3 and described above, a top plate and bottom plate are paired and operate to grip adjoining busway housing sections together and the top and bottom plates that are utilized to create the gripping force are smooth. In contrast, in the present invention a coupling system is disclosed with a markedly roughened surface on an area of one or more those portions of the top and/or bottom plate that are intended to contact and grip the busway housing. The components having such a roughened surface are preferably formed of a selected material which indents the contacted surface of the busway housing, thereby substantially increasing the amount of gripping force and increasing substantially the force necessary to separate the joined housing sections.
The roughened surface operates to increase the co-efficient of friction between the busway housing section and the top and/or bottom plates. The roughened surface may be in the form of serrations or other indentations on the surfaces of the top and/or bottom plates contacting the busway housing sections, or may be in the form of materials adhered to or formed within the surfaces, such as grits or other materials. The materials adhered to the surface may be adhered by any known process, including welding, soldering, brazing, chemical or other adhesives and the like. A particularly preferred embodiment comprises serrations in either the top or bottom plate of a material sufficiently rigid to deform the busway housing section when the busway housing section is clamped between the top and bottom plate. In an alternative embodiment of the present invention, the busway housing itself may also include a roughened surface on that portion of its surface contacting the top and bottom plates to further increase the co-efficient of friction between the top plate, bottom plate and the busway housing section gripped therebetween.
In one embodiment of the invention, the connecting assembly of the present invention is used to connect the bottoms of the adjoining housing sections together, but not the tops of the adjoining housing sections. In an alternative embodiment of the present invention connecting assembly of the present invention is used to connect the tops of the adjoining housing sections together but not the bottoms. In yet another embodiment of the present invention the novel connecting assembly of the present invention is used on both the top and bottom portion of interface between the two housing sections. Finally, as may be appreciated, the novel connecting assembly of the present invention may be used with wrap-around type connector assemblies illustrated in FIG. 2 as well the orientations of top, bottom and side are generally illustrated in FIG. 1A.